In recent years, about 500 oil spills have occurred in the Prudhoe Bay oil fields and along the 800-mile pipeline each year, according to the Alaska Department of Environmental Conservation, even though the daily "throughput" of oil has declined from about 2 million barrels a day in 1987 to less than half that today. Most leaks are minor, quickly detected, and remedied.
But in March, the largest leak in North Slope production history – as many as 267,000 gallons – poured out of a corroded pipeline at the Prudhoe Bay complex for five days before being discovered. Since then, US EPA investigators have been seeking to determine whether BP violated the federal Clean Water Act by failing to prevent corrosion in the ruptured line. If it did, criminal charges could follow.